1. Department
of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
2. Center
for Structural Biology, Vanderbilt University, Nashville, Tennessee 37232, United States
3. Department
of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, United States
4. Departments
of Chemistry, Pharmacology, and Bioinformatics, Vanderbilt University, Nashville, Tennessee 37232, United States